Technology Tales

Adventures & experiences in contemporary technology

Running cron jobs using the www-data system account

22nd December 2018

When you set up your own web server or use a private server (virtual or physical), you will find that web servers run using the www-data account. That means that website files need to be accessible to that system account if not owned by it. The latter is mandatory if you you want WordPress to be able to update itself with needing FTP details.

It also means that you probably need scheduled jobs to be executed using the privileges possess by the www-data account. For instance, I use WP-CLI to automate spam removal and updates to plugins, themes and WordPress itself. Spam removal can be done without the www-data account but the updates need file access and cannot be completed without this. Therefore, I got interested in setting up cron jobs to run under that account and the following command helps to address this:

sudo -u www-data crontab -e

For that to work, your own account needs to be listed in /etc/sudoers or be assigned to the sudo group in /etc/group. If it is either of those, then entering your own password will open the cron file for www-data and it can be edited as for any other account. Closing and saving the session will update cron with the new job details.

In fact, the same approach can be taken for a variety of commands where files only can be access using www-data. This includes copying, pasting and deleting files as well as executing WP-CLI commands. The latter issues a striking message if you run a command using the root account, a pervasive temptation given what it allows. Any alternative to the latter has to be better from a security standpoint.

Online learning

18th April 2021

Recently, I shared my thoughts on learning new computing languages by oneself using books, online research and personal practice. As successful as that can be, there remains a place for getting some actual instruction as well. Maybe that is why so many turn to YouTube where there is a multitude of video channels offering such possibilities without cost. What I have also discovered is that this is complemented by a host of other providers whose services attract a fee and there will be a few of those mentioned later in this post. Paying for online courses does mean that you can get the benefit of curation and an added assurance of quality in what appears to be a growing market.

The variation in quality can dog the YouTube approach and it also can be tricky to find something good even if the platform does suggest new videos based on what you have been watching. Much of what is on there does take the form of webinars from the likes of the Why R? Foundation, RStudio or the NHSR Community. These can be useful and there are shorter videos from such providers as the Association of Computing Machinery or SAS Users. These do help more if you already have some knowledge about the topic area being discussed so they may not make the best starting points for someone that is starting from scratch.

Of course, working your way through a good book will help and it is something that I have been known to do but supplementing this with one or more video courses really adds to the experience and I have done a few of these on LinkedIn. That part of the professional platform came from the acquisition of Lynda.com and the topic areas range from soft skills like time management through to computing skills courses with R, SAS and Python seeing coverage among the data science portfolio. Even O’Reilly has ventured into the area in an expansion from the book publishing activities for which so many of us know the organisation.

The available online instructor community does not stop at the above since there are others like Udacity, Programiz, Udemy, Business Science and Datanovia. Some of these tend towards online education provision that feels more like an online university course and those are numerous as well as you will find through Data Science Central or KDNuggets. Both of these earn income from advertising to pay for featured blog posts and newsletters while the former also organises regular webinars and was my first port of call when I became curious about the world of data science during the autumn of 2017.

My point of approach into the world of online training has been as a freelance information professional needing to keep up to date with a rapidly changing field. The mix of content that is both free of charge and that which attracts a fee is one that can work. Both kinds do complement each other while possessing their unique advantages and disadvantages. The need to continually expand skills and knowledge never goes away so it is well worth spending some time working what you are after since you need to be sure that any training always adds to your own knowledge and skill level.

Work locally, update remotely

4th December 2008

Here’s a trick that might have its uses: using a local WordPress instance to update your online blog (yes, there are plenty of applications that promise to edit your online blog but these need file permissions to the likes of xmlrpc.php to be opened up). Along with the right database access credentials and the ability to log in remotely, adding the following two lines to wp-config.php does the trick:

define('WP_SITEURL', 'http://localhost/blog');

define('WP_HOME', 'http://localhost/blog');

These two constants override what is in the database and allow to update the online database from your own PC using WordPress running on a local web server (Apache or otherwise). One thing to remember here is that both online and offline directory structures are similar. For example, if your online WordPress files are in blog in the root of the online web server file system (typically htdocs for Linux), then they need to be contained in the same directory in the root of the offline server too. Otherwise, things could get confusing and perhaps messy. Another thing to consider is that you are modifying your online blog so the usual rules about care and attention apply, particularly with respect to using the same version of WordPress both locally and remotely. This is especially a concern if you, like me, run development versions of WordPress to see if there are any upheavals ahead of us like the overhaul that is coming in with WordPress 2.7.

An alternative use of this same trick is to keep a local copy of your online database in case of any problems while using a local WordPress instance to work with it. I used to have to edit the database backup directly (on my main Ubuntu system), first with GEdit but then using a sed command like the following:

sed -e s/www\.onlinewebsite\.com/localhost/g backup.sql > backup_l.sql

The -e switch uses regular expression substitution that follows it to edit the input with the output being directed to a new file. It’s slicker than the interactive GEdit route but has been made redundant by defining constants for a local WordPress installation as described above.

Why are there no savings on buying software using electronic distribution, Adobe?

15th March 2007

If you ever potter over to Adobe’s online software store, a curious anomaly awaits you: electronic download editions of their software are never cheaper than the equivalent boxed versions. In fact, there are cases where the electronic version costs more than the boxed one. One would have thought that ditching the box, the disc(s) and whatever accompanies them would save Adobe money and they would pass this onto you but it does not seem to make its way into the pricing for some reason. Another thing is that selling direct should allow Adobe to undercut retailers and make more money from their software but it is the likes of Amazon that have the better prices. Whatever way you look at it, you have to admit that this pricing model doesn’t make a lot of sense.

Some online writing tools

15th October 2021

Every week, I get an email newsletter from Woody’s Office Watch. This was something to which I started subscribing in the 1990’s but I took a break from it for a good while for reasons that I cannot recall and returned to it only in recent years. This week’s issue featured a list of online paraphrasing tools that are part of what is offered by Quillbot, Paraphraser, Dupli Checker and Pre Post Seo. Each got their own reviews in the newsletter so I will just outline other features in this posting.

In Quillbot’s case, the toolkit includes a grammar checker, summary generator, and citation generator. In addition to the online offering, there are extensions for Microsoft Word, Google Chrome, and Google Docs. In addition to the free version, a paid subscription option is available.

In spite of the name, Paraphraser is about more than what the title purports to do. There is article rewriting, plagiarism checking, grammar checking and text summarisation. Because there is no premium version, the offering is funded by advertising and it will not work with an ad blocker enabled. The mention of plagiarism suggests a perhaps murkier side to writing that cuts both ways: one is to avoid copying other work while another is the avoidance of groundless accusations of copying.

It was appear that the main role of Dupli Checker is to avoid accusations of plagiarism by checking what you write yet there is a grammar checker as well as a paraphrasing tool on there too. When I tried it, the English that it produced looked a little convoluted and there is a lack of fluency in what is written on its website as well. Together with a free offering that is supported by ads that were not blocked by my ad blocker, there are premium subscriptions too.

In web publishing, they say that content is king so the appearance of an option using the acronym for Search Engine Optimisation in it name may not be as strange as it might as first glance. There are numerous tools here with both free and paid tiers of service. While paraphrasing and plagiarism checking get top billing in the main menu on the home page, further inspection reveals that there is a lot more to check on this site.

In writing, inspiration is a fleeting and ephemeral quantity so anything that helps with this has to be of interest. While any rewriting of initial content may appear less smooth than the starting point, any help with the creation process cannot go amiss. For that reason alone, I might be tempted to try these tools from time to time and they might assist with proof reading as well because that can be a hit and miss affair for some.

 

Buying OEM Vista?

27th January 2007

A few days ago, I mused over buying OEM Vista if/when the time came for me to do upgrade. Then, I came to the conclusion that OEM was a no-no unless you bought it installed on a system. In an article on the PC Magazine website, things seem not to be as cut and dried as that. Apparently, the perceived wisdom is that if you are building a system for yourself and you agree to provide all support as the system builder to yourself as the system user, then everything is OK under the licence. Also, there seems to be a trend among resellers that it is not them who are subject to the terms of the licence but the customers who purchase the OEM software. It is all just a little bit confusing. Draw your own conclusions…

Online favicon.ico creation

21st January 2008

I recently updated the icon that appears beside this blog’s address in the address bar and bookmarks menus of some browsers. I gave it a go in GIMP but I seemed to get no joy. I pottered out on the web to discover what I might have done wrong only to find Dynamic Drive offering online favicon.ico creation. Out of curiosity, I decided to give the thing a whirl and download the result to upload onto my web server. GIF’s, JPG’s PNG’s and BMP’s with a size less than 150 KB are accepted and it did work for me.

Refurbished Computers

12th July 2014

Refurbished Computers

While I never have been a home user of refurbished or second hand kit, there are those who do and there do appear to be some bargains to be had. For some reason, I get the sense that computing and photographic hardware seems to heading more upmarket as time goes on so it may be that this becomes the only way of getting cheaper computers unless you stick with Chromebooks and their like. Interestingly, the now defunct Micro Mart magazine did a feature on the subject and even Apple has legitimised the idea with its presence.

Manufacturers

Apple

With the premium reputation that Apple has, the chance of bagging any sort of a bargain from them is too good to overlook and they have had a refurbished goods store for longer than many. There are no iPhones here but Macs, iPads and iPods are made available in this way so it is worth a look. The chance of a cheaper Mac of some sort is a tempting idea.

Dell

A colleague of mine at work swears by this so much that it is where he looked when buying a laptop for his father. There are home and business sections too so even servers are available along with laptop and desktop PC’s as well as tablets.

Resellers

eBuyer

This is a computer kit reseller who I have never used so far but there have been qualms expressed about their customer service. Like many, they too have a clearance section so it may be worth a look if fancy taking a little risk.

Morgan

The mainstay of this lot are pre-used computers and they have been around a while too, even if they disappeared from the web for a while at one stage. They also had a shop near Manchester’s Piccadilly train station though I am left wondering if any of the apparent bargains tempted anyone.

Specialists

Giga Refurb
MicroDream
Pure IT Refurbished
Tier1online.com
Itzoo

These have the quality of their work approved by Microsoft themselves so there should be some confidence here. With Microsoft having put Windows XP out to grass, Windows 7 is being promoted on machines with at least Intel Core 2 Duo CPU’s and prices can be very reasonable too.

Cheaper retail Vista?

2nd February 2007

Brain Livingston has described an intriguing way to go using the retail Upgrade editions of Vista to do a fresh installation without having either windows 2000 or XP installed in the latest edition (free – there is a paid version but I veer away from information overload) of the Windows Secrets email newsletter: install it twice! After the first time around, it cannot be activated because there is no previous version of Windows installed but it is possible to do a Vista to Vista "upgrade", the second installation, and that can be activated. It is strange behaviour but I suppose that it placates those who think that the full retail packages are far too expensive. They even think that in the U.S.; but "rip off" Britain is getting a lot worse deal because we are not seeing the benefits of the low dollar at all. If right was right, we should be getting Vista at half of the price that we are paying for it. It’s enough to drive you to going the OEM option or not upgrading at all, especially since XP is going to be supported until 2011 (I have seen 2014 mentioned in some places). Livingston is going to cover the whole OEM discussion in the next edition of Windows Secrets and I for one will be very interested to see what he has to say.

Never undercutting the reseller…

23rd October 2009

Quite possibly, THE big technology news of the week has been the launch of Windows 7. Regular readers may be aware that I have been having a play with the beta and release candidate versions of the thing since the start of the year. In summary, I have found to work both well and unobtrusively. There have been some rough edges when access files through VirtualBox’s means of accessing the host file system from a VM but that’s the only perturbation to be reported and, even then, it only seemed to affect my use of Photoshop Elements.

Therefore, I had it in mind to get my hands on a copy of the final release after it came out. Of course, there was the option of pre-ordering but that isn’t for everyone so there are others. A trip down to the local branch of PC World will allow you to satisfy your needs with full, upgrade (if you already have a copy of XP or Vista, it might be worth trying out the Windows Secrets double installation trick to get it loaded on a clean system) and family packs. The last of these is very tempting: three Home Premium licences for around £130. Wandering around to your local PC components emporium is an alternative but you have to remember that OEM versions of the operating system are locked to the first (self-built) system on which they are installed. Apart from that restriction, the good value compared with retail editions makes them worth considering. The last option that I wish to bring to your attention is buying directly from Microsoft themselves. You would think that this may be cheaper than going to a reseller but that’s not the case with the Family Pack costing around £150 in comparison to PC World’s pricing and it doesn’t end there. That they only accept Maestro debit cards along with credit cards from the likes of Visa and Mastercard perhaps is another sign that Microsoft are new to whole idea of selling online. In contrast, Tesco is no stranger to online selling but they have Windows 7 on offer though they aren’t noted for computer sales; PC World may be forgiven for wondering what that means but who would buy an operating system along with their groceries? I suppose that the answer to that would be that people who are accustomed to delivering one’s essentials at a convenient time should be able to do the same with computer goods too. That convenience of timing is another feature of downloading an OS from the web and many a Linux fan should know what that means. Microsoft may have discovered this of late but that’s better than never.

Because of my positive experience with the pre-release variants of Windows 7, I am very tempted to get my hands on the commercial release. Because I have until early next year with the release candidate and XP works sufficiently well (it ultimately has given Vista something of a soaking), I’ll be able to bide my time. When I do make the jump, it’ll probably be Home Premium that I’ll choose because it seems difficult to justify the extra cost of Professional. It was different in the days of XP when its Professional edition did have something to offer technically minded home users like me. With 7, XP Mode might be a draw but with virtualisation packages like VirtualBox available for no cost, it’s hard to justify spending extra. In any case, I have Vista Home Premium loaded on my Toshiba laptop and that seems to work fine, in spite of all the bad press that Vista has gotten for itself.

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